1. Field of the Invention
The present invention relates to a technique of an air bag as one of safety devices for a vehicle and, more particularly, a technique of an air bag useful to protect a passenger in a transport vehicle from a front or side impact.
2. Description of the Related Art
In recent years, the installation rate of an air bag as one of safety parts for a vehicle is rapidly increasing in association with growing awareness of safety of an occupant. An air bag is useful to protect an occupant by sensing an impact by a sensor at the time of a collision of the vehicle, generating high-temperature and high-pressure gas from an inflator, and deploying the air bag rapidly.
Conventionally, air bags for protecting an occupant at the time of a collision from a front impact are installed for a driver side and a passenger side. Recently, an air bag capable of dealing with an impact from a side has been developed. An air bag for each of the driver""s side and the passenger side is conventionally manufactured by sewing two base fabrics for an air bag. However, recently, for improvement in performance of an air bag and reduction in manufacturing cost, attention has been being paid to a hollow weaving technique capable of forming a bag at a weaving stage.
In many cases, an air bag for side-impact protection is designed in consideration of roll over of a vehicle. Different from the air bags for the driver side and the passenger side, it is necessary to assure internal pressure holding time of several seconds to about ten seconds after deployment. It is designed so that the head of an occupant can be protected even during roll over of a vehicle. Consequently, a gas leak from the woven fabric body (hereinbelow, also called xe2x80x9cair leakxe2x80x9d) has to be prevented. A sewn product is not practical since an air leaks from a seam. Under present circumstances, the surface of a base fabric for a hollow-woven air bag is usually coated.
In the case of hollow-woven air bags for the driver side and passenger side, it is unnecessary to bold the internal pressure for several seconds to about 10 seconds, so that an uncoated fabric is usually used to realize light weight and compactness. For this purpose, a high-density woven fabric of low permeability is necessary. All of hollow-woven air bags for driver side, passenger side, and side-impact protection have a big problem such that, when the air bag is inflated, air leaks from deviation in a boundary portion between a single layer that is interwoven by the same yarn (fastened portion) and a bag portion and residuals jump out from the inflator. In order to solve the problem, a high-density woven fabric is necessary as a material.
Moreover, at the present stage, in many cases, a side-impact protection hollow-woven air bag base fabric is designed in consideration of roll over of a vehicle, and an air bag obtained by coating the surface of the hollow-woven air bag base fabric to improve the internal pressure holding performance of the bag is used. However, a base fabric for an air bag having the internal pressure holding performance resistive to roll over of a vehicle does not exist conventionally.
For example, Japanese Unexamined Patent Application No. Hei-4-193646 discloses a technique of dividing a single structure that is interwoven by the same yarn of the hollow-woven air bag into the inner side and the outer side and applying weave structures of different restraints of warps and wefts to the inner and outer sides. However, the difference of restraints between the inner and outer sides is not defined, and the proposal does not sufficiently obtain the inner pressure holding performance requested at the time of deployment of the air bag.
Paying attention to the problems of the conventional base fabric for a hollow-woven air bag and, particularly, improvement in the internal pressure holding performance, an object of the present invention is to provide a base fabric for a hollow-woven air bag which solves the problem of air leak from the boundary between a bag portion and a fastened portion.
A base fabric for a hollow-woven air bag according to the invention is characterized by comprising:
a bag portion (multiple fabric portion) formed by connecting a plurality of cloth pieces by hollow weaving;
a fastened portion A connected to the bag portion (multiple fabric portion); and
a fastened portion B of a weave structure different from that of the fastened portion A, which is formed in a boundary portion between the bag portion (multiple fabric portion) and the fastened portion A.
With the configuration, by inserting a special structure band to the boundary portion between the bag portion and the fastened portion A, the deviation in the boundary portion when the air bag is expanded is reduced, leak of gas generated from the inflator can be prevented with reliability, and the improved internal pressure holding performance of the air bag can be accordingly achieved. As a result, the base fabric for a hollow-woven air bag capable of solving the problem of air leak from the boundary portion between the bag portion and the fastened portion can be provided.
Preferably, the fastened portion B has 1 to 20 warps and/or wefts.
With the configuration, the air leak from the fastened portion B as the boundary portion between the bag portion and the fastened portion is further prevented.
Preferably, the weave structure of the fastened portion B is that warps and/or wefts of at least one line existing in the boundary face with the bag portion are interlaced in the order opposite to that of the end line of the bag portion.
Preferably, the weave structure of the fastened portion B is that warps and/or wefts of at least one line existing in the boundary face with the fastened portion A are interlaced in the order opposite to that of the end line of the fastened portion A.
According to the invention, there is also provided a base fabric for a hollow-woven air bag, comprising
a bag portion (multiple fabric portion) formed by connecting a plurality of cloth pieces each made by warps and wefts by hollow weaving,
wherein a rate of variation in a crimp ratio of all of the warps is 40% or less.
With the configuration, the rate of variation in the crimp ratio between the warps in the portions of different weave structures is low. Consequently, occurrence of loosening of the warps during weaving can be suppressed, improved weaving performance can be accordingly obtained, and the base fabric of high quality is obtained. In the case of coating the surface of the base fabric, uniform coating is performed, and improved internal pressure holding performance of the air bag can be achieved.
Preferably, a rate of variation in thickness in the width direction of the base fabric for an air bag is 3% or less.
With such a configuration, flatness of the base fabric is achieved and the number of defects caused by a crease decreases. Further, since the flatness of the base fabric is obtained, post-treatment is excellently performed. Even in the case where coating is necessary in post-treatment, since the ability of coating is good, the internal pressure holding performance of the air bag can be further improved.
Preferably, a rate of variation in a crimp ratio of all of the warps is 30% or less, more preferably, 15% or less, and most preferably, 10% or less.
According to the invention, there is also provided an air bag comprising
a base fabric for an air bag for forming a bag portion, and
an inflator attaching port provided for the bag portion,
wherein the base fabric for an air bag comprises:
the bag portion (multiple fabric portion) formed by connecting a plurality of cloth pieces by hollow weaving;
a fastened portion A connected to the bag portion (multiple fabric portion); and
a fastened portion B of a weave structure different from that of the fastened portion A, which is formed in a boundary portion between the bag portion (multiple fabric portion) and the fastened portion A.
With the configuration, the air bag solving the problem of the air leak from the boundary portion between the bag portion and the fastened portion can be provided.
Alternately, the air bag may be constructed by comprising
a base fabric for an air bag for forming a bag portion and
an inflator attaching portion provided for the bag portion,
and the base fabric for an air bag has the bag portion (multiple fabric portion) formed by connecting a plurality of cloth pieces each made by warps and wefts by hollow weaving, and a rate of variation in a crimp ratio of all of the warps is 40% or less.
With the configuration as well, the base fabric of high quality with improved internal pressure holding performance of the air bag can be obtained.
According to the invention, there is also provided a side-impact protection air bag comprising:
a base fabric for an air bag for forming a bag portion; and
an inflator attaching port provided for the bag portion,
wherein the base fabric for an air bag comprises
the bag portion (multiple fabric portion) formed by connecting a plurality of cloth pieces made by warps and wefts by hollow weave, and
a rate of variation in crimp ratio of all of the warps is 40% or less.
Since the rate of variation in the crimp ratio between warps in portions of different weave structures is low, occurrence of loosening of warps during weaving can be suppressed, the weaving performance is improved, and the base fabric of high quality is achieved. Consequently, the side-impact protection hollow-woven air bag of high quality with improved internal pressure holding performance of the air bag can be obtained.
Preferably, a rate of variation in thickness in the width direction of the base fabric for an air bag is 3% or less.
With the configuration, the weaving performance is improved and a rate of variation in thickness in the width direction of the base fabric is low. Thus, the flatness of the base fabric is achieved, the number of defects such as a crease decreases, and post-treatment can be excellently performed. Also in the case where coating is necessary in post-treatment, coatability thereof can be performed more excellently.